This invention relates generally to conveyor diverting systems, and more particularly to conveyor diverting systems having an endless conveying surface composed of multiple surface members, each one or group of adjacent ones mounted with a laterally movable shoe capable of diverting packages or other articles from the conveying surface by pushing laterally against the articles as they move down the conveyor. Such lateral pushing diverts a package from a main conveyor to an adjacent branch conveyor, or other receiving structure.
Conveyor diverting systems using a moving conveying surface consisting of a plurality of parallel surface members have been known for a number of years. Such diverting systems utilize a diverter shoe movably mounted on one or more of the surface members for lateral movement with respect to the conveying surface under the guidance of a track network. Such a system is disclosed, for example, in commonly-assigned U.S. Pat. No. 5,127,510 issued to Cotter et al., and commonly-assigned U.S. Pat. No. 5,165,515 issued to Nitschke et al., the disclosures of which are hereby incorporated herein by reference. The track network is located generally under the conveying surface and guides the diverter shoes via follower portions descending from the diverter shoes and engaging the track network. Diverters or diverter switches in the track network selectively transfer guidance of each diverter shoe from a track running in the direction of the movement of the conveying surface to a diagonal track, or plurality of diagonal tracks, in order to cause lateral movement of the diverter shoes. Examples of diverter switches used to selectively transfer guidance of diverter shoes between tracks are disclosed in U.S. Pat. No. 5,409,095, issued to Hoshi et al., and U.S. Pat. No. 5,039,912, issued to Cotter, and International Publication No. WO 01/83342 A1 by Bozarth et al. In order to avoid wasted spacing between variable-length packages, such diverting systems may include manual or automatic measuring means at an infeed point to cause the diverter gate associated with the selected branch conveyor to divert a selected number of shoes corresponding in general to the length of the package. Exemplary of this type of conveyor are U.S. Pat. No. 3,361,247, issued to James N. Lauzon et al. and U.S. Pat. No. 4,738,347, issued to Brouwer, the latter being commonly assigned with the present invention.
The diverters or diverter switches used to divert the shoes onto diagonal tracks are often desirably spaced apart approximately the same distance as the distance between adjacent surface members. This spacing allows adjacent diverters to divert shoes along adjacent surface members. Such spacing, however, often leaves little room for the diverter switches. In order to construct diverter switches that can operate in such spaces, it is often necessary to construct the diverter switches so that they divert shoes at a relatively steep angle. That is, the diverter switches are constructed so that they change the motion of the shoes from a state in which the shoes are traveling longitudinally with no transverse motion to one in which they have a relatively high transverse motion component. In general, the steeper the angle at which the diverter switches divert shoes in a transverse direction, the more space that is created for the physical structure of the diverting gate to occupy. Diverting the shoes at too steep of an angle, however, can cause difficulties as will be set forth in more detail below.
With increased demands for the number of packages to be conveyed by such conveying systems, the overall speed of the conveyor has become an important factor in the design of conveying systems. As a general matter, increasing the speed of the conveyor typically increases the throughput of the conveyor. Increasing the speed of the conveyor, however, can create other difficulties. For example, if the longitudinal speed of the conveyor is increased, the lateral speed of the diverter shoes will also increase during package diverts. If this lateral speed gets too great, however, the diverter shoes may impinge the package with such force that the package is toppled, knocked backwards on the conveyor, knocked off of the conveyor, or otherwise undesirably moved. While the lateral speed of the diverter shoes can be decreased by lessening the angle of the diverting tracks, as noted above, decreasing the angle of the diverting tracks may not leave sufficient room for the diverter switches to be operably installed. Also, decreasing the divert angle generally requires the adjacent take-away conveyors to take up more space in order to accommodate the greater effective width of the article when it is diverted at a smaller angle. Having larger take-away conveyors not only increases their expense, but also uses up more factory floor-space, which is often at a premium. Further, the need can therefore be seen for a diverting conveyor that mitigates the aforementioned problems associated with increased conveyor speeds.
Increased demands for package throughput also make the amount of inter-package spacing an important factor. By spacing packages closer together, more packages can be placed on a conveyor, and thus more packages can typically be processed over a given time period when they are spaced more closely together. However, a minimum inter-package spacing is desirable as a result of the rotation of a diverted package as it is diverted. Because of this rotation, additional inter-package spacing is required to avoid conflict between the package being diverted and a closely trailing package. This rotation pushes the trailing corner of the package adjacent the branch conveyor back a distance. Sufficient spacing between the packages to accommodate the backward movement of this corner is desirably included in conveyor systems. The extent of this spacing, however, is desirably reduced, and the need can be seen for a conveyor diverting system that can more effectively decrease the amount of necessary inter-package spacing.